1. Field of the Invention
The present invention relates to internal combustion engines and, more particularly, to an internal combustion engine having a superior cycle comprised of three events, namely, compression, combustion, and ventilation, accomplished in two strokes with greater efficiency than has heretofore been made available through the prior art.
2. Description of the Background
Many internal combustion engines operate on a cycle known as the Otto Cycle which has been known since as far back as the year 1801. Whether one is explaining the operation of a two cycle engine or a four cycle engine, the Otto Cycle defines four basic events that occur within the engine during the cycle, namely, intake (or induction), compression, power (or ignition), and exhaust.
In a four stroke engine, approximately one stroke (180 degrees of the 720 degree cycle) is devoted to each event. While modern high speed four stroke engines have attempted to incorporate near simultaneous intake and exhaust, these events still require two separate strokes in a four stroke engine. In such an arrangement, all of the airflow occurs at the top of the cylinder, which tends to help to cool the cylinder head, but which fails to cool the cylinder body. Further, in such a configuration, the power stroke can comprise at best no more than 22% of the cycle, thus limiting the overall power output potential of the engine.
In a two stroke engine, power, exhaust, and intake all occur on the down stroke, followed by additional exhaust and compression on the up stroke. The familiar two stroke internal combustion engine defines four distinct events within the combustion cylinder during its cycle. Beginning with the ignition of the fuel/air mixture in the cylinder, pressure rises above the cylinder head to drive the piston downward through the cylinder. While traveling downward through the cylinder, the piston uncovers an exhaust port to expose the cylinder (which is under high pressure) to near atmospheric pressure, and the combustion products previously held within the cylinder force themselves out of the cylinder through the exhaust port. The piston continues its downward travel through the cylinder to then uncover an intake port prior to the piston reaching its bottom dead center position. During the return stroke (or "up stroke"), the intake port is first closed by the piston. However, for at least a brief period, the exhaust port remains open as the piston continues to travel upward in its return stroke. Thus, some of the fresh air taken in through the intake port and a portion of any fuel that has thus far been mixed into that air is likewise forced out of the exhaust port until the piston closes the exhaust port by passing it during its return stroke. Once the exhaust port is closed, the remaining air and fuel mixture is compressed. Once compression is completed, the two cycle process is finished, and ignition of the fuel/air mixture occurs once again to start the cycle anew. Unfortunately, the period of the cycle during which the piston travels from its bottom dead center position to the top of the exhaust port results in a significant loss of fresh air and fuel which could be used as part of the combustion product.
Another feature of a typical two stroke engine is that the crankcase in a two stroke engine provides a volume of space in which much of the carburetion takes place. This configuration prevents the use of a volume of oil splashing around in the crankcase as is normally the case with a traditional four stroke engine. Thus, in a two stroke engine, oil must be mixed with the fuel prior to its introduction into the cylinder, creating either an additional burden on the user who must mix the fuel and oil prior to use, or requiring more complex fuel and oil delivery systems, while producing an environmentally unfriendly exhaust product which includes burnt oil as a combustion byproduct.
It would therefore be advantageous to provide an improved internal combustion engine which enables the air being inducted into a combustion chamber to participate in cooling the entire cylinder, which increases the efficiency of previously known two cycle engines without requiring the complexity and additional weight associated with four cycle engines, and which prevents the need to use a fuel/oil mixture in a two cycle engine configuration.